This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to 01107137.0 filed in Europe on Mar. 22, 2001; the entire content of which is hereby incorporated by reference.
This invention relates to an apparatus for controlling the discharge of flowable material from a first compartment that has a discharge opening near a lower end thereof. A closure member is movable between a closed position in which it shuts this discharge opening and a raised open position in which it opens an annular gap of a certain width around the discharge opening to allow said flowable material to flow through said gap and said discharge opening. There are conveying walls adjoining the discharge opening for providing a predetermined path of conveying the flowable material, when flowing through the discharge opening, into a second compartment in communication with the conveying path. An actuating device moves the closure member from its closed position into its open position and vice-versa. Furthermore, there is an adjusting device for adjusting the width of the above-mentioned annular gap. Support means in the path of the conveying walls hold both the actuating and the adjusting devices.
Such an apparatus is disclosed in U.S. Pat. No. 6,123,233 which is hereby incorporated in its entirety. In an apparatus of this type, the flowable material is of a certain sensitive or hazardous nature and may consist of powdery vitamins or also dangerous dust, e.g. chemicals or even radioactive substances. The term of xe2x80x9ccompartmentxe2x80x9d should be considered in its broadest sense and may encompass conveying vessels, bins, conveying conduits, mixers, reactors or process and reaction zones (e.g. in a chemical process). The terms xe2x80x9cfillingxe2x80x9d and xe2x80x9cconcentrationxe2x80x9d, as used below, should be understood in their broadest meaning.
Although U.S. Pat. No. 6,123,233 describes a specific and especially advantageous actuating device, the present invention is not restricted to it, but could also use bellows, cylinders or other actuators.
From E-A-29 23 444, WO 90/08724 and U.S. Pat. No. 4,691,843, which are incorporated in their entirety, it is known to vary the gap of the closure member by varying its open top position. However, all these known designs are constructed in such a way that, in order to vary this gap, a fitter had to have access into the interior of the bin or vessel. This is, of course, not possible while the material flows out. Thus, the operation of the bin or vessel had to be interrupted, and the latter had to be dismantled so that the fitter could reach the interior. It is clear, that it could even be dangerous for a filter because of possible contact with hazardous substances. When the fitter is in the interior, he cannot check the effect of his adjustment onto the flow properties of the material and, therefore, adjustment can only be effected very roughly and arbitrarily. One could only determine whether the adjustment was correct or insufficient during operation. In addition, bulk material in a vessel may assume a different consistency over time. The result may be that the adjustment and position chosen is first suitable, but later the flow properties change over time. However, varying the position of the closure member during operation is not possible with the known designs.
From DE-A-29 23 444, WO 90/08724 and U.S. Pat. No. 4,691,843, it is known to vary the gap of the closure member by varying its open top position. However, all these known designs are constructed in such a way that, in order to vary this gap, a fitter had to have access into the interior of the bin or vessel. This is, of course, not possible while the material flows out. Thus, the operation of the bin or vessel had to be interrupted, and the latter had to be dismantled so that the fitter could reach the interior. It is clear, that it could even be dangerous for the man to contact there the hazardous substances. When the fitter is in the interior, he cannot check the effect of his adjustment onto the flow properties of the material and, therefore, adjustment can only be effected very roughly and arbitrarily, and one can only determine whether the adjustment was correct or insufficient during operation. In addition, bulk material in a vessel may assume a different consistency over time. The result may be that the adjustment and position chosen is first suitable, but leads to varying flow properties over time in one or the other sense. However, varying the position of the closure member during operation is not possible with the known designs.
Therefore, it is an object of the present invention to enable or, at least, facilitate precise fine metering without the necessity of interrupting the operation.
This object is achieved by providing a quantity determining device for determining the amount of flowable material flown to the second compartment, and a control arrangement for controlling at least the adjusting means and the width of said gap to achieve a desired degree of delivery to the second compartment. Although it is preferred to have the control effected automatically by connecting the quantity determining device to the control arrangement, this is not necessary under all circumstances; for example, it could be sufficient that the quantity determining device merely indicates the amount of flowable material flown to the second compartment or degree of delivery by measuring a related value so that an operator can accordingly handle the control arrangement. The amount of flowable material flown to the second compartment can be determined either more or less directly by weighing or measuring volume of the material, or indirectly by determining the concentration of the material in a process zone, by measuring the pH, a temperature change caused by the material or by using a Geiger detector or the like.
The use of an actuator of variable gap is, in principle, known from the above-mentioned DE-A-29 23 444, WO 90/08724 and U.S. Pat. No. 4,691,843. To add an adjustment device to an invariable actuator is known per se by U.S. Pat. No. 6,123,233. However, to combine them with a control which is able of controlling the adjustment device during operation, i.e. during filling, in such a manner that the flow of flowable material can be controlled by selecting the width of the discharge gap is the xe2x80x9cmissing linkxe2x80x9d which enables precise dosing and metering.
In principle, it would be conceivable to have the control arrangement acting onto both the actuator and the adjustment device, for example in the sense of a cascade control wherein the adjustment device is controlled into an extreme position and the actuator is used for setting the desired gap width (or vice-versa, the actuator moves into a predetermined position, while the adjustment device adjusts the gap width which is preferred).
Particularly in the case of a vertical arrangement, e.g. as according to U.S. Pat. No. 6,123,233, the construction according to the invention also be used for loosening the bulk material in the first compartment by raising and lowering the actuator relative quickly, thus achieving the effect of a vibrator, i.e. promoting flow of the material. In this way, a separate vibrator can be omitted. This can be done automatically, if desired, if the control arrangement is formed to control also the loosening device. Such loosening device can also be formed, as is known per se, be air nozzles in the region of the top of the closure member, i.e. on it or around it.
In any case, the quantity determining device for determining the actual degree of filling and (or) concentration, e.g. in a second vessel docked to the conveying path of the first vessel, in the case of a manual operation, it is possible to read the indication of the degree and to close the closure member, when a desired degree has been reached.
However, it is also possible to chose a wider discharge gap if it turns out that the gap width normally used leads to too long a filling time. To this end, it is useful if the quantity determining device comprises a timer for determining the degree per time unit.
All these functions cane be automated, if the control arrangement comprises a comparator stage for comparing the degree preset by a presetting device with a value related to the actual degree determined by the quantity determining device.